Water washing of contaminated soil using solutions of surfactants and chelating agents is known. Such systems use substantial volumes of liquid water to dissolve or wash away contaminants from the surface of the bulk soil particles.
In other decontamination systems, volatile contaminants are removed by vaporization with steam under conditions which maintain the steam and the entrained contaminant in the vapor phase for removal by vacuum or vapor flow means.
Separation of particulate materials and segregation by size is well known. A variety of devices and systems are known. For example, spiral separators, vibrating screens and sieves and the like.
Soil washing is a volume reduction technique for treating soil or other particulate materials contaminated by a variety of chemical and physical agents such as oils, chemical waste etc. The particulate material is slurried with water and subjected to one or more stages of scrubbing with classification according to particle size between successive stages. Separation of the washed coarser particles from the more highly contaminated fine particles achieves a substantial reduction in the volume of material requiring further treatment or disposal.
Soil washing techniques are based on the theory that the contaminants are concentrated in fine size portion of the material and that the contaminants associated with the coarser or larger size particles tend to be associated with the surface of the particle.